Cast core clamp



April 12, 1949 A. F. METTERMAIER CAST GORE CLAMP Filed Dec.

Inventor: Armin Fil littehmaien by I ZZO

His At torney.

Patented Apr. 12, 1949 CAST CORE CLAMP Armin FlMittermaier, Fort Wayne, Ind., assignor to General Electric Company, a corporation of New York Application December 4, 1947, Serial No. 789,684

1 Claim.

This invention relates to a, cast clamp and more particularly to a cast clamp for electrical induction apparatus having a magnetic core structure comprised of stacked punched laminations.

Certain lossesin iron cored induction devices can be reduced by making the core out of punched laminations. When this is done it is necessary to use some type of clamping arrangement to hold the stacked laminations together. In the case of small type induction apparatus the conventional means of binding the laminations is to use a prefabricated clamp which is installed by using a nut and bolt causing the laminations to be pressed together. This method, or any similar method using a prefabricated clamp has the disadvantage of involving two processes. One, the manufacture of the clamp, two, the installation of the clamp.

It is well known in the art that the more firmly the laminations are bound together the less will be the power losses and the vibratory noises.

In accordance with this invention the manufacture and installation of the core clamp are combined into one operation, and the laminations are bound more firmly together than has hitherto been the case.

- An object of this invention is to provide a new and improved method for clamping together the laminated core structure of electrical induction apparatus by incorporating into one operation the fabrication and installation of the clamp.

Another object of the invention is to decrease the power losses and noise due to vibration by more firmly binding the laminations together.

Still another object of the invention is to provide a simple means for casting a one piece clamp which will bind together the laminated core structure of electrical induction apparatus.

Still another object of the invention is to provide a means for insuring the fastness of the cast clamp.

The invention will be better understood from the following description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claim.

Fig. 1 is a perspective view of a preferred form of the invention incorporated as the clamping means for a fluorescent lamp ballast. Fig. 2 is a front elevation of the fluorescent ballast showing temporary adjustable clamping arrangement and the mold preparatory to casting the clamp. Fig. 3 is a cross-section of the balast and temporary adjustable clamping device taken through the section 33 of Fig. 2.

Referring now to Fig. 1 there is shown therein by way of example a fluorescent lamp ballast I constructed from stacked laminations 2 of a ferro-magnetic material and made up in three partsthe core outer legs 3 and 4 and the core center leg 5 which has on it three coils 5, I, and 8 of copper wire or other metal of high conductivity. Binding the laminations 2 and the three core sections 3, 4 and 5 together are two cast metal clamps 9 and i0. Clamp 9 is shown in a cutaway section revealing keyhole grooves H in two of the three main sections. There is a similar groove in the third section 4 and one in the opposite end of each of the three sections 3, 4, and 5.

It is necessary before attempting to join the main core sections 3, 4 and 5 together as a unit to tightly stack the properly aligned laminations 2, and, then, securely hold the three main core sections 3, 4 and 5 in firm proximity to one another. This is done in the following manner.

The laminations 2 of the core center leg 5 are stacked, and on the core center leg 5 are placed the three coils 6, l and 8. In order to firmly hold the laminations together a wedge M of wood or other suitable material is driven between, in the illustrated case, coil 2 and the stacked laminations 2. The laminations which make up the outer core legs 3 and t are stacked and aligned, and these as well as the already prepared center core section 5 are placed in a temporary adjustable clamping device 23 similar to that shown in Figs. 2 and 3. The two outer core legs 3 and 4 fit into C-shaped clamps 54 having screws l5 passing through them which when tightened press together firmly the stacked laminations 2. in order to firmly hold together the three core sections 3, 4 and 5 another c-shaped clamp 96 which rests against the clamps 14 in the manner shown in Fig. 2 is used, so that by tightening the screw I! which presses against one of the clamps 15, the three main core sections 3, 4 and 5 are forced together. This can be better seen in Fig. 3. It will be noted in Fig. 2 that the clamps l3 and I4 are shorter in length than the main core sections 3, 4 and 5 of the ballast. This is to allow for the installation of the permanent clamp 9. Since the clamp 9 is cast its manufacture and installation are combined into one operation. A split mold made up of two similar sections l8 and I9 is placed over the exposed end of the three main core sections 3, 4 and 5, and into the mold l8 and I9 is poured molten type metal 20 or some other similar non-magnetic material such as babbltt having a relatively low melting point and which contracts as it cools and hardens. When the metal 20 hardens it is securely fastened to the laminated portions of the ballast. -Additional fastening means such as keyhole grooves Ii may be supplied in the core to provide for locking keys which are formed as an integral part of the clamp 9. In cooling the metal 29 contracts and binds the laminations 2 more firmly together as well as forcing the three main core sections 3, I and 5 into more positive contact. Clamp III is cast in a similar manner When both clamps l and I0 have hardened in position the temporary adjustable clamp I3 is removed by loosening the screws II and I1 and the mold l8 and I9 is separated from the casting 20 by pulling=on hooks which are passed through the hookeyes 2i and 22.

While there has been shown and described a particular embodiment of this invention it will be obvious to those skilled in the art that various 20 m r changes and modifications can be made therein without departing from the invention and, therefore, it is aimed in the appended claim to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure b Letters Patent oi the United States is: In combination, a generally rectangular mag- .netic core having at least two abutting laminated ARMIN F. mTI'ERMAIER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Re. 14,113 Thordarson Apr. 18, 1916 1,085,116 Ford Jan. 27, 1914 1,629,132 Thordarson May 17, 1927 1,711,414 Kanaky Apr. 30, 1929 2,083,395 Pfalzgrafl. June 8, 1937 

